It sounds as though it needs a line of sight from the rear to the chamber ? If that's the case I'm not sure how it would be set up for use on something like a M1 / M1A which has a solid rear receiver.
It seems there's some moving parts that will have to re-position very accurately to be able to...
I think the aim is to be able to recheck zero without firing ? It sounds a bit like overkill to replace bore sighting, if it works.
2-3 shots at 20 yards will get you close enough to move out to 100 to sight.